The present invention relates to a rotating blade for use in a turbomachine such as a gas turbine. More specifically, the present invention relates to a gas turbine rotating blade having a handling device for directing cooling air for the blade cooling air passages.
The turbine section of a gas turbine includes a rotor that is comprised of a series of disks to which blades are affixed. Hot gas from the combustion section flows over the blades, thereby imparting rotating power to the rotor shaft. In order to provide maximum power output from the gas turbine, it is desirable to operate with gas temperatures as high as possible. However, operation at high gas temperatures requires cooling the blades. This is so because the strength of the material from which the blades are formed decreases as its temperature increases.
Traditionally, turbine blades are cooled by flowing cooling air through the blades. Typically, the cooling air is extracted from the air discharging from the compressor section, thereby bypassing the combustion process, and directed to the turbine rotor. The rotor directed the cooling air to the roots of the blades. From the blade root, the air is directed to flow through a number of cooling passages formed in the airfoil portion of the blade. These passages typically terminated at openings formed in the surface of the blade, such as at the tip and the leading and trailing edges. Thus, after cooling, the spent cooling air was discharged to the hot gas flowing through the turbine section and discharged from the turbine exhaust. Such a turbine blade cooling scheme is shown in U.S. Pat. No. 5,117,626 (North et al.), hereby incorporated by reference in its entirety. In this approach, it is often difficult to properly distribute the cooling air to the various cooling passage inlets formed in the root portion of the blade.
Moreover, recently, efforts have been aimed at developing closed loop cooling systems in which the spent cooling air is returned to the compressor discharge air, or directly into the combustor, for incorporation into the combustion process. Alternatively, a closed loop cooling system may be utilized in which the spent cooling air is cooled and returned to the turbine rotor for further cooling. Unfortunately, such closed loop cooling air systems further exacerbate the air handing problem, since not only must the supply cooling air be distributed to the cooling passages but the discharged cooling air must be collected from the cooling air passages for return to the system. This additional air handling problem can further complicate the geometry of the cooling passages within the blade.
It is therefore desirable to provide a device for distributing cooling air to the cooling air passages of a turbine blade and, in closed loop systems, for collecting the spent cooling air from the cooling passages as well.